This invention relates to a miniature motor, such as a stepping motor, used in printers and facsimile machines, and more particularly to a miniature motor in which an improvement is made so that the ends of coils as the components of the stator are easily held in position and connected to power feeding lead wires.
Stepping motors as one type of miniature motors have heretofore been widely used as a drive source for various types of equipment, such as information processing equipment. One type of stepping motor has such a construction that two coils as the components of the-stator are disposed coaxially in the axial direction of the motor, as disclosed in Japanese Published Unexamined Patent Application No. Sho-61 (1986)-4459.
FIG. 1 is a longitudinal sectional view illustrating a stepping motor of a conventional type. In FIG. 1, reference numeral 1 refers to a housing formed of a metallic material, such as mild steel, into a bottomed hollow cylindrical shape, on the inner circumferential surface of which yokes 2 formed of a ferromagnetic material into an annular shape, coil bobbins 3 formed of an insulating material into an annular shape, and coils 4 wound on the coil bobbins 3 are provided. Numeral 5 refers to an end plate fitted to an open end of the housing 1.
Numeral 6 refers to a rotor formed of a permanent-magnet material, such as ferrite, into a cylindrical shape and having a plurality of magnetic poles extending axially, which are disposed radially on the outer circumferential surface thereof. Numeral 7 refers to a shaft fixedly fitted to the axial center of the rotor 6 and rotatably supported by bearings 8 provided on the housing 1 and the end plate 5.
With the aforementioned construction, as current is fed to the coils 4 via control equipment (not shown), the yokes 2 are excited by a combination of 2-phase currents flowing in the coils 4, driving the rotor 6 having a plurality of magnetic poles disposed on the outer circumferential surface thereof to cause to rotate in short and uniform angular movements, thus transmitting power to driven equipment in accordance with the short and uniform angular movements.
The coil 4 used in a stepping motor having the aforementioned construction is manufactured by winding a predetermined number of turns of a coil wire as the material of the coil 4 on the coil bobbin 3 with an end of the coil wire being secured, applying adhesive on the wound coil wire surface to prevent the wound coil wire from being frayed, and cutting the wound end of the coil wire. The winding operations up to this stage can be carried out a special purpose machine or a general purpose industrial robot, for example.
Next, a predetermined length of lead wire is connected by soldering to an end of each coil wire, and each connected part is covered with an insulating tape to ensure electrical insulation. Then, the entire wound coil wire surface is further covered with an insulating tape, with the lead wires being run along the wound coil wire surface, to prevent excessive tensile force from being exerted on the connected parts and ensure electrical insulation over the entire coil wire surface.
Aside from the preceding process of winding the coil wires on the coil bobbins 3 in the aforementioned coil winding process of the conventional type, the succeeding process of connecting lead wires to the coil wires wound on the coil bobbins involves low workability and efficiency because of reliance on manual operations.
To solve the above problems, a means of providing terminal pins on the outer periphery of the coil bobbins 3 and wrapping and soldering the ends of coil wires constituting the coils 4 onto the terminal pins has been proposed (refer to Japanese Published Unexamined Utility Model Application No. Hei-4 (1992)-4716). FIG. 2 is a cross-sectional view illustrating the essential part of an example of such a means. Like parts are indicated by like numerals in FIG. 1.
In FIG. 2, the coil bobbin 3 has a core 31 formed into a hollow cylindrical shape, and flanges 32, of a larger outside diameter than the outer diameter of the core 31, formed integrally at both end faces in the axial direction of the core 31. A terminal 33 having terminals 10 and a common terminal 11 is provided on any one of the flanges 32. To wind a coil 4, a wire leader 41 of a coil 4 is connected to any one of the terminals 10, and a wire tail end 42 thereof to the common terminal 11. Then, a wire leader 41 of another coil 4 constituting another phase is connected to the common terminal 11, and a wire tail end 42 thereof to the other terminal 10. The housing 1 has a notch 12 to allow the terminal 33 to protrude outward from the housing 1.
Whereas the aforementioned arrangement facilitates the coil winding operation considerably, but still requires cumbersome operations of soldering lead wires to the terminals 10 and the common terminal 11, leading to low workability. When mounting connectors on the terminals 10 and the common terminal 11, the connectors being mounted have to be held in proper positions. This entails troublesome operations and low reliability in terms of strength in the mounting and connecting parts.